1. Field of the Invention
The present invention relates to an operating mechanism of medical device with an auxiliary driving force that assists a load-side manipulation input using a driving force, and a medical manipulator including the operating mechanism.
2. Description of Related Art
Conventionally, in manipulation devices of surgical robots, a manipulation arm with an auxiliary driving force is known. The manipulation arm is a member that assists manipulation of an operator with a driving force using a driving mechanism, such as a motor, and makes an operational feeling of an operator light, or the like, improving an operational feeling.
In the manipulation arm with an auxiliary driving force, torque is applied to the manipulation arm from the driving mechanism. However, if friction or backlash in the gears of the driving mechanism is transmitted to the operator, an operational feeling is deteriorated instead. Thus, controlling the torque applied to a load side, such as the manipulation arm, from the driving mechanism has been studied.
As an example, a mechanism that controls torque is described in Non-Patent Document 1 “A Study on the Torque Control of a DC Motor with Reduction Gears” by Kazuo Tanie et al, Collection (Edition C) of Papers of Japan Society of Mechanical Engineers, Volume 54, No. 503, pp 1515-9, Jul. 1988. In this mechanism, a torque sensor is installed at an output shaft, and torque control is performed by feeding back the output of the torque sensor to a motor current. However, a strain gauge torque sensor that is being used has problems with stability, noise tolerance, or the like when the torque sensor is a portion of the output shaft.
In order to solve the above problems, a mechanism that performs torque control using the detection of positional information only is described in Non-Patent Document 1 “A Study on the Torque Control of a DC Motor with Reduction Gears”. In this mechanism, elastic bodies are inserted into the output shaft instead of the torque sensor, and an encoder, which detects the rotational angle of the output shaft on the motor side of the elastic bodies and the rotational angle of the output shaft on the load side, is provided. Then, torque control is performed by performing feedback based on the values of these rotational angles.